Many of the fancy goldfish strains are bred with egg-shaped bodies. This unnatural body shape predisposes them to buoyancy problems. Goldfish that experience buoyancy problems are not able to control their position in the water correctly. These cold-water fish often flip into an upside-down position and may float at the water surface. Individual fish are forced into a head- or tail-standing position and select goldfish sink to the bottom of the aquarium. The aquarist can assist goldfish that have sunk and remain on the substrate by making a buoyant sling for these fish.
Draw a rough sketch of the affected goldfish's shape, paying very careful attention to the position and number of fins. Make the drawing life size and as accurate as possible.
Cut out the outline of the goldfish you have just drawn and place it on a piece of 100 per cent cotton flannel.
Cut out a piece of 100 per cent cotton flannel in the shape of the goldfish outline. Cut the piece large enough so it can fold over the back of your fish.
Examine your living goldfish very carefully and use this image, together with the drawing, to cut out sections of the flannel that coincide with the position of the fish's fins.
Cut out a section that coincides with the position of the vent of the fish.
Use the tip of the scissors to make a small hole in each of the four corners of the piece of flannel.
Thread a 6-inch piece of string through each hole and tie a knot in the string to secure each piece to the flannel.
Tie a small fish bobber to the free end of each of the four pieces of string.
Use the tip of the scissors to make a small hole on the right hand side of the flannel, at a point approximately one-quarter down the length of this side. Make a second small hole, approximately three-quarters down the length of this side.
Repeat this process on the left hand side of piece of flannel.
Rinse your hands to remove any traces of soap or hand cream, which is detrimental to the water and the populations of beneficial bacteria.
Wet the flannel sling.
Retrieve your goldfish from the bottom of the aquarium, either with an aquarium net, or with your hand.
Place the goldfish carefully into the sling and request an assistant to fold the right and left sides over the back of the fish.
Request the assistant to thread a 4-inch piece of string through the holes closest to the fish's head and to tie a knot. The assistant needs to thread a 4-inch-long piece of string through the holes toward the piece of flannel as well.
Gently release the fish in the aquarium. The weight of the fish will allow it to sink into the water, but the fishing bobbers will keep it afloat.